Use CAMLnoreturn_{start,end} instead of Noreturn

[nojb]

This fixes compilation under MSVC, see

https://github.com/ocaml/ocaml/blob/4e9eb755e60d0f0f4e458eb3f7af26bce5d8e2ba/runtime/caml/misc.h#L52-L61

[nojb]

Friendly ping

[nojb]

Thanks! Sorry for the lag, but this macro does not seem to be available on 4.02... is that a problem?

[smorimoto]

I personally believe that supporting MSVC would be more valuable than keeping 4.02 support, but I don't know why this fails in 4.02. If I remember correctly, it would have been available even with 4.02.

[nojb]

I personally believe that supporting MSVC would be more valuable than keeping 4.02 support, but I don't know why this fails in 4.02. If I remember correctly, it would have been available even with 4.02.

We could continue to use Noreturn for 4.02 (if there is an easy way to test for the OCaml version using the C preprocessor).

[smorimoto]

Yes, that sounds good, but is there a way to make a special version constraint only on Windows? Otherwise, I think it would be clean to drop 4.02.

[MisterDA]

There is, see https://ocaml.org/manual/intfc.html#ss:c-internal-macros. Just opened a PR to restore Noreturn on 4.02.

Some parts of Lwt already don't support 4.02.

- lwt_ppx → ppxlib >= 0.16.0 → ocaml >= 4.04.1
    base of this switch (use `--unlock-base' to force)

In #843 I suggested to raise the minimum requirement on 4.06 (edit: at least on Windows).

[smorimoto]

Oh, my "IIRC" proved wrong again here!
If we raise the downward version constraint on Windows, the #887 seems not necessary. And I would like to +1 to making it happen.